Since its formation, Retroviral Diseases Section has conducted research on human immunodeficiency virus (HIV) disease, in addition to our studies on HIV-associated malignancies. The studies on HIV have for a number of years focused on the HIV protease and the GagPol protease precursor. We have explored the feasibility of developing a novel therapy to HIV protease through inhibition of HIV protease dimerization. HIV protease is a dimer composed of two identical monomers. Our group previously found that glutathiolation of a conserved cysteine (Cys 95) at the HIV protease dimer interface abolishes HIV-1 protease activity. This suggested that the dimer interface and inhibition of dimerization could be a novel target for drug development. We showed that several peptides could be designed that interfered with HIV protease dimerization and that this peptide could block HIV viral production from infected cells. We have also explored the effect of these inhibitors on the Gag-Pol polyprotein, which needs to form a dimer and self-cleave itself to form active protease. Our hypothesis is that such dimerization inhibitors may be optimally directed at this initial dimerization of the Gag-Pol polyproteins. We have developed an in vitro translation assay to study inhibitors of the first autocleavage of HIV GagProPol, and have found that it is modified by oxidation of cysteines in the protease sequence, although somewhat differently than mature protease. In addition, we are exploring the effects of various protease inhibitors on this first autocleavage step. We have found that the protease inhibitor darunavir also has activity in inhibiting HIV protease dimerization. During the past year, we have been collaborating with Dr. Mitsuya's group on studies of the entry of novel HIV protease inhibitors into the brain, using an in vitro system. In addition, in a new collaboration with Dr. Marjorie Robert-Guroff in NCI, we have been developing a novel technique to sort HIV virions using flow cytometry. Finally, in collaboration with Drs. Maldarelli and Hughes in NCI, we have been studying the oligoclonal nature of HIV integration in patients on long-term anti-HIV therapy.